Which combination correctly describes the classical 'triple deformity' of the knee in advanced tuberculosis of the knee joint?

• A Flexion, anterior subluxation, and varus angulation
• B Extension, anterior subluxation, and internal rotation
• C Flexion, posterolateral subluxation, and external rotation ✓
• D Abduction, extension, and external rotation

Explanation

As tuberculous knee arthritis progresses, effusion and muscle spasm produce fixed flexion. Relaxation of the cruciate ligaments and capsular distension allow the tibia to subluxate backwards and laterally behind the femoral condyle, producing external rotation of the limb. This flexion, posterolateral subluxation and external rotation combination is the classical triple deformity. Anterior subluxation and internal rotation are not features of this process.

Reference: Bailey and Love's Short Practice of Surgery, 27th ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

Written and medically reviewed by the StethoPrep medical team.